As microwave energy becomes increasingly present in our environment, an unmonitored population is placed at risk while we must admit to insufficient data regarding the biologic effect of such exposure. The basic aim of this project will be to determine the effects of a long term (4 months) exposure to microwave radiation (MWR) at low incident power densities. Our intent will be to examine the behavioral effects of administratively safe MWR (i.e., less than 10 mW/cm2 incident power density). Data will be obtained from several behavioral variables, and we will define a dose/response curve over the range of 0-20 mW/cm2. The chronic MWR environment will comprise individual RF chambers into which control and experimental animals will be individually introduced for 3-4 hours of whole body MWR exposure per day. Pulse modulated MWR at 1.3 GHz will be used. In the first part of this study, the effects of 0, 2, 5, 10, and 20 mW/cm2 MWR on open field behavior and on instrumental behavior for food reward will be determined in rats. Besides the 0 mW/cm2 group, additional control groups will be exposed to a mild thermal and acoustic stress. In the second part of this study and to initiate the extrapolation of the results to human exposure, the changes in instrumental behavior relevant to learning will be determined. Again, dose/response curve will be defined, via radiation at 5, 10, and 20 mW/cm2 with dual control groups, as above. These studies will provide new and needed data regarding the origin of chronic low level MWR effects on cognitive behavior and learning.